The present invention relates to field of microwave thermal therapy of tissue. In particular, the present invention relates to a coolant-sensor interface module for enabling temperature and pressure of a liquid coolant within a thermal therapy catheter fluid supply system to be sensed.
Benign prostatic hyperplasia (BPH) may be treated using transurethral thermal therapy as described in further detail in U.S. Pat. No. 5,413,588 entitled DEVICE FOR ASYMMETRICAL THERMAL THERAPY WITH HELICAL DIPOLE MICROWAVE ANTENNA and in U.S. patent application Ser. No. 08/309,137 entitled COOLANT PRE-CHILLING PRIOR TO BENIGN PROSTATIC HYPERPLASIA TREATMENT, both assigned to Urologix, Inc., which are herein incorporated by reference. During transurethral thermal therapy, tumorous tissue growth within the prostate surrounding the urethra is heated to necrose the tumorous tissue to treat BPH. Transurethral thermal therapy is administered by use of a microwave antenna-containing catheter which includes a multi-lumen shaft. Energization of the microwave antenna causes the antenna to emit electromagnetic energy which heats tissue within the prostate. To avoid unnecessary and undesirous damage to the urethral and adjacent healthy tissues, the catheter is provided with cooling lumens through which liquid coolant circulates to control the temperature distribution of tissue surrounding the catheter.
Typically, the liquid coolant is supplied to the thermal therapy catheter by a pump which pumps the liquid coolant from a reservoir through the thermal therapy catheter. Conventional liquid coolant supply systems comprise relatively large reservoirs containing as much as five gallons of liquid coolant from which liquid coolant is supplied to the thermal therapy catheter. The liquid coolant contained within the large reservoir is simply maintained at room temperature. Although the liquid coolant being circulated through the thermal therapy catheter experiences a temperature increase during thermal therapy, such increases are relatively insignificant due to the large volume of liquid contained in the reservoir. However, conventional liquid coolant supply systems have failed to provide for precise, closed loop control of the temperature and pressure of the liquid coolant being supplied to the thermal therapy catheter. In addition, conventional liquid coolant supply systems are expensive and require extensive and time consuming sterilization between a treatment of different patients.